The present invention relates to printers and more particularly to dot matrix printers of the impact type utilizing means for directly inking the print wire tips as a greatly simplified alternative to the conventional technique of printing through the use of inked ribbons.
Dot matrix printers typically utilize liquid printing materials such as printing ink as the means for printing on a print receiving medium. The ink may either be applied to the print receiving medium by a technique in which the ink is propelled toward the print receiving medium, which technique is used in ink jet printers, or the ink may be transferred from a ribbon saturated with ink to the print receiving medium by impacting a printing element such as a print wire against the inked ribbon to transfer ink from the inked ribbon to the print receiving medium, forming printed data in the shape or contour of the surface portion of printing element striking the inked ribbon. The latter type of printers are typically referred to as impact type printers.
The disadvantages of the above printer designs are set forth in copending Ser. No. 901,182 filed Apr. 28, 1978, now U.S. Pat. No. 4,194,846, issued Mar. 25, 1980 and assigned to the assignee of the present application. The disadvantages of the above printer designs pointed out in the abovementioned U.S. Pat. No. 4,194,846 have led to the development of a printing device as described in said patent which is adapted to deliver liquid printing material from a container to be directed to the tips of the print wires which transfer the liquid printing material to a print receiving medium when said tips impact against said print receiving medium. Although this design eliminates the disadvantages encountered in ink jet printers and encountered in printers using conventional inked ribbons, it has been found that the apparatus described by the said U.S. Pat. No. 4,194,846 lacks the ability to accurately regulate the amount of ink delivered to the print wires which leads to dripping and smudging of the ink resulting in an overall degradation in print quality. In addition, it has been found that the ink in the apparatus of the abovementioned U.S. Pat. No. 4,194,846 dries out prematurely, making the design both impractical and uneconomical.